Velocity and Flame Wrinkling Characteristics of a Transversely Forced, Bluff-Body Stabilized Flame, Part II: Flame Response Modeling and Comparison with Measurements

Abstract

This article analyzes the response of bluff-body stabilized flames to transverse acoustic waves. Data were obtained for bluff-body flames at flow velocities of 50m/s and 100m/s with inlet air temperatures ranging from 475-750K. Two different modes of acoustic excitation were applied, corresponding to velocity and pressure nodes/antinodes along the combustor centerline. High-speed imaging and phase-locked particle image velocimetry (PIV) were used to characterize the spatio-temporal flame front and velocity field response. The key objective of the study is to compare measurements of the fluctuating velocity and flame wrinkling using the G-equation, e.g., to compare how the ensemble averaged unsteady flame wrinkling gain/phase predicted by solving the G-equation using the measured velocity field as inputs compares to the measured values. These results show good qualitative agreement between the comparisons and measurements, and quite good quantitative accuracy in many of the cases. These comparisons also enable insight into the features controlling the unsteady flame wrinkling; for example, it enables insight into the relative contributions of acoustic and vortical disturbances on the flame wrinkling characteristics, whose different propagation velocities lead to interference patterns and oscillatory flame wrinkle amplitude characteristics.